Bottom hole pump



Aug 4, 197() A. P. BENTLEY ETAL 3,522,996

BOTTOM HOLE PUMP Filed Jan. 2, 1969 4 Sheets-Sheet l Fig. o

lo'rf;

7 INVENTORS El ARTHUR P BENTLEY e glas DAVID KANE www 'ITORNEYS Aug.. 4, 1970 A R BENTLEY ETAL 3,522,996

BOTTOM HOLE PUMP 'ITORNEYS ug. 4, 197() A, P, BENTLEY ET AL 3,522,996

BOTTOM HOLE PUMP Filed Jan. 2, 1969 4 Sheets-Sheet I5 EXHAUST INVENTORS se ARTHUR P. BENTLEY a DAVID KANE o@ BY M40 *x7/WU ATTORNEYS All? SUPPLY Aug. 4, 1970 A, P BENTLEY ET AL 3,522,996

BOTTOM HOLE PUMP Filed Jan. 2, 1969 4 Sh sa .3] E 1 ML/ 3 y Q1.. INVENTORS '2 ARTHUR P. BENTLEY 8 DAVID KANE BY JM@- www ATTORNEYS United States Patent O U.S. Cl. 417-404 12 Claims ABSTRACT OF THE DISCLOSURE This specification discloses a pump designed for operation in the bottom of an oil well under the influence of air or gas delivered thereto from the earths surface. The pump consists essentially of an actuating cylinder and piston assembly that is located in the Well bore above the bottom. The pistons of this assembly are connected to a tubular pump rod which extends downwardly into a pumping cylinder in which it is connected to a pump piston. The actuating assembly comprises a fixed partition on the opposite sides of which are a pair of pistons. The latter reciprocate on a pair of tubular strain rods. An air inlet is positioned in one strain rod and terminates in the partition. An inlet valve is operatively installed in the partition and directs air to one side or the other of said partition to render the air under pressure effective on the piston at that side. The bore of the other strain rod functions as an exhaust and an exhaust valve in the partition establishes communication between the exhaust and one side or the other of the partition. The pump piston reciprocates in the pumping cylinder and has an axial passage communicating with the tubular pump rod. Radial passages extend from the axial passage to the outer cylindrical surface of the pump piston and O rings floating in annular grooves function as check valves controlling the flow of oil from the pumping cylinder into the axial passage therein.

The present invention relates to pumps that are installed in a well bore near the bottom thereof for the purpose of raising oil to the earths surface and is concerned primarily with improvements in the cylinder and piston actuating mechanism of such a pump as well as a novel pumping piston and cylinder.

The primary object of the present invention is to provide a pump that is susceptible of installation in a well casing having a diameter in the nature of four inches and which is operable under the influence of air or gas under pressure from the earths surface. In attaining this end a pump is provided that includes two characteristic elements. One of these is the cylinder and piston assembly constituting the actuating mechanism and the other is the pumping cylinder and piston which is disposed in the lowermost position with the piston being connected to the actuating mechanism by a pump rod.

In outlining certain more detailed objects and advantages of the invention it will be assumed there is a well casing extending from the earths surface to the well bottom. A tubular conduit for receiving air under pressure is positioned in this casing and terminates at the actuating mechanism. An exhaust line in the casing extends from the actuating mechanism to a point above the oil level. An oil delivery conduit is located centrally of the casing and extends from the actuating mechanism to the earths surface.

An important object is to provide, in a pump of the type noted, actuating mechanism comprising upper and lower heads carrying an air cylinder with a pair of tubular strain rods in opposed diametric positions extending between the heads. A tubular pump rod extends axially 3,522,996 Patented Aug. 4, 1970 through the air cylinder and projects through the upper head into the oil delivery conduit.

A partition is ixedly secured to the air cylinder midway thereof and defines upper and lower chambers. The pump rod is slidably received in a central opening in the partition. A piston reciprocates in the upper chamber and is slidable over the strain rods. It is anchored to the pump rod. Another piston reciprocates in the lower chamber. It also slides on the strain rods and is affixed to the pump rod. The bore of one strain rod communicates between the air supply and a valve in the partition. The bore of the other strain rod communicates between an exhaust valve in the partition and the exhaust line.

An important object is to provide, in a pump actuating mechanism of the character aforesaid, a new and improved air inlet valve which is actuated by engagement of the pistons in the air cylinder to direct air alternately into the upper and lower chambers. This valve comprises a stem carrying a valve disc and springs are associated with the opposite ends of the stem so that energy is stored therein when engaged by a piston with the spring moving the disc to its other position when a piston reaches a limit of movement. This results in a rapid change of the valve position at the same time cushioning the action.

Another object is to provide, in pump actuating mechanism of the type noted, a new and improved exhaust valve which alternately exhausts air from the chambers. This valve is of the spool type and is also spring cushioned.

The pumping cylinder is spaced below the actuating mechanism. This cylinder includes a top wall to which is secured the lower end of a spacer. The latter comprises a central tube extending from the lower head of the actuating mechanism to the lower end of the spacer. The pump rod passes through this tube. A plurality of supports are disposed about the central tube.

Another highly important object is to provide, in a pump of the kind described, a pumping cylinder and piston assembly comprising a top ring that is anchored to the spacer end, a pumping cylinder depending from the ring opening to a bottom end wall formed with a recess communicating with the well bottom, a bypass line from the bottom end wall to the top ring, a check valve at the upper end of the bypass, a check valve in the bottom end wall controlling flow from the recess to the pumping cylinder, and a pumping piston in the cylinder and aixed to the lower end of the pump rod.

Another object is to provide, in a pumping cylinder and piston assembly of the type noted, a pumping piston comprising a cylindrical body having a central passage opening into the top face thereof and closed at its lower end. The body is formed with at least one annular groove and radial passages communicate between this groove and the central passage. An O ring is positioned in the groove in floating relation to the walls thereof and functions as a check valve permitting flow of oil from the cylinder through the radial prassage to the central jassage upon movement of the piston in only one direction.

Various other more detailed objects and advantages of the invention such as arise in connection with carrying out the above noted ideas in a practical embodiment will in part become apparent and in part be hereinafter stated as the description of the invention proceeds.

For a full and more complete understanding of the invention reference may be had to the following description and accompanying drawings wherein:

FIG. l is a vertical section through an oil Well casing depicting the elements of the subject pump in elevation;

FIG. 2 is a horizontal section taken about on the plane represented by the line 2-2 of FIG. l;

FIG. 3 is a horizontal section through the spacer, being taken about on the plane represented by the line 3-3 of FIG. 1;

FIG. 4a is a vertical section through the actuating mechanism;

FIG. 4b is a vertical section through the spacer and the upper end of the pumping cylinder;

FIG. 4c is a vertical section through the remainder of the pumping cylinder, depicting the pumping piston in elevation;

FIG. 5 is a horizontal section through the actuating mechanism, being taken about on the plane represented by the line 5-5 of FIG. 4a;

FIG. 6 is a compound section taken on an enlarged scale and about on the planes represented by the lines 6-6 of FIG. 5;

FIG. 7 is a detailed perspective depicting the air inlet valve on an enlarged scale;

FIG. 8 is a similar perspective of the exhaust valve; and

FIG. 9 is an axial section through the pumping cylinder and piston assembly with the cylinder being illustrated in an exaggerated longitudinally compacted condition.

GENERAL ASSEMBLY An oil well hole is shown at 10 in FIG. l as extending vertically into an earth body 11. The hole 11 is lined with a casing 12 having a bore 13. An oil delivery conduit 14 is positioned centrally of the bore 13 and extends from the surface of earth 11 to the actuating mechanism that is identified in its entirety at A. A supply line for air or gas under pressure is shown at 15. It also extends from the earths surface to actuator A. The level of oil in casing 12 is depicted at 16. An exhaust line 17 extends from the actuator A to a point above the level 16. ln accordance with conventional practice a packer 1S is positioned in bore 13 above the oil level 16. The conduit 14 and air line 15 pass through the packer 18.

A spacer is referred to in its entirety by the reference character S. It is located below the actuator A and above a pumping assembly indicated at P.

THE ACTUATING MECHANISM Referring now more particularly to FIG. 4a the actuator A comprises an upper head 19 formed with a socket 20 opening onto its upper face and which receives the lower end of conduit 14. This connection is xed as by welding at 21. Also opening onto the upper face of head 19 are threaded sockets 22 and 23 in substantially diametrically opposed relation. The exhaust line 17 is screwed into the socket 22 and the air supply line 14 into the socket 23. The head 19 is formed with an axial passage 24 which opens into the socket 20, a threaded passage 25 which communicates with the socket 22 and another threaded passage 26 which communicates with the socket 23.

The head 19 is cut away at its inner or lower end to form an outer corner annular recess on which is tted the upper end of an air cylinder 27. An O ring 28 seals this connection. A tubular pump rod 29 reciprocates in the passage 24 and its upper end projects into the conduit 14. O rings 30 seal this sliding connection. A hollow strain rod 31 has its upper end threaded and screwed into the passage 25, thus becoming a part of the exhaust line. Another hollow strain rod 32 has its upper end threaded and screwed into passage 26. A smali air conduit 33 is received in the bore of strain rod 32 and its upper end communicates with air supply line 15. The strain rod 32 is formed with ports 34 adjacent to head 19.

A partition 35 is xedly secured in the cylinder 27 as by welding 36. It is formed with a central passage 37 which slidably receives pump rod 29. O rings 3S seal this sliding tit.

Referring now to FIGS. 5 and 6, the partition 35 is formed with a through passage 39 which receives strain rod 31. O rings 40 seal this connection. The passage 39 is enlarged midway the faces of partition 35 to provide an annular recess 41. Radial ports 42 communicate between recess 41 and the bore of strain rod 31. Partition 35 is formed with a socket 43 opening onto its top face and another socket 44 opening onto its bottom face. These sockets 43 and 44 are connected by a passage 45 which is smaller than the sockets and thus presents shoulders 46 and 47 at its opposite ends.

A spool valve is designated in its entirety by the reference character V. It is the exhaust valve and comprises two complemental parts 48 and 49. Valve part 48 has a head which slides in the socket 43 with an O ring -50 sealing the sliding tit. It is also formed with a spring seat 51 which receives one end of a compression coil spring 52.

Valve part 49 also has a head received in socket 44 and an O ring 53 seals this sliding lit. A spring seat 54 opens onto the lower face of valve part 49 and a spring 55 is received therein. Partition 35 cooperates with cylinder 27 in defining an upper chamber 56 and a lower chamber 57. The springs 52 and 55 project into these chambers respectively where they are susceptible of engagement by pistons to be later described.

Valve part 48 has a shank 58 (FIG. 8) while valve part 49 has a shank 59. These Shanks are connected by the threaded stud and socket connections shown in FIG. 6. The outside diameter of the Shanks 58 and 59 is less than the diameter of the passage 45 to provide a space about either shank which is received in passage 45. Partition 35 is formed with an opening 60 which communicates with annular recess 41 and lbore of passage 45.

Thus with the valve V in the position depicted in FIG. 6 communication is established between lower chamber 57 and the bore of strain rod 31 via socket 44, passage 45, opening 60, annular recess 41 and ports 42. When the valve V is in the opposite position, this communication is interrupted by the head of valve part 49 being snugly received in the socket 44. At the same time the head of valve part 48 is removed from socket 43 and communication between upper chamber 56 and the bore of strain rod 31 is established.

As shown in FIGS. 5 and 6 partition 35 is formed with another through passage 61 receiving the strain rod 32. O rings at 62 seal this connection. A solid rod 63 is positioned in the strain rod 32 below the partition 35 and its upper end terminates in a disc like head 64 that closes the bore of the strain rod 32. The lower end of air supply conduit 33 abuts disc 64 and is thereby closed. The portion of conduit 33 at its lower end is enlarged to provide a snug tit with the bore of strain rod 32. O rings 65 seal this connection. Air conduit 33 has radial openings 66 opening onto an annular recess 67 formed in the thickened part of conduit 33 between O rings 65.

Partition 35 is formed with an openign 68 which is enlarged at 69 with a shoulder 70 between the two. A passage 71 communicates between annular recess 67 and enlarged opening 69.

An inlet valve is designated generally I. As shown in FIG. 7 it comprises an enlarged body portion 72 that reciprocates in enlarged opening 69 (FIG. 6). O rings 73 seal this sliding t. Extending upwardly from body 72 is a stem 74 the outer portion of which is formed as a sleeve 75 which receives a spring 76` Openings 77 communicate between the interior of the sleeve adjacent the lower end thereof and the space in opening 69 about stem 74.

Partition 35 is countersunk about the upper end of opening 69 and a ring 78 is positioned in the countersink and secured in position by screws 79. Sleeve 75 extends through ring 78 and spring 76 projects into upper chamber 56 above ring 78. Another stem 80 extends from the lower side of body 72 and terminates in a sleeve 81 receiving a spring 82. The latter projects beyond sleeve 81 into lower chamber 57. Parts 83 communicate between the interior of 81 and the space about stem 80 in opening 68.

Partition 35 has a Vertical passage 84 which extends from the upper face of the partition to a horizontal passage 85 that opens into the bore of strain rod 32 below disc 64. It also has another vertical passage 86 extending rom the lower face of the partition to a horizontal passage 87 that opens onto the bore of strain rod 32 just above the thickened end of air conduit 33.

In the position of FIG. 6 air from conduit 33 passes through ports 66 into annular recess 67. From the latter it goes through passage 71 into the space in opening 69 about stem 74. From this space it passes through ports 77 into sleeve 75 and out the open end of the latter into chamber 56.

When valve I is moved to its opposite position the passage 71 opens onto the other side of valve body 72 into the space about stern 80 which then will be positioned in opening 69. It passes from the latter through ports 83 and sleeve 81 to the lower chamber 57.

Referring now to the right hand side of FIG. 4b air cylinder 27 is shown as having its lower end anchored in a recess in the corner of a lower head 88. An O ring 89 seals this connection. Head 88 has a central opening 90 which slidably receives pump rod 29. O rings 92 seal this sliding it. Strain rod 31 passes through an opening 93 in head 88 and projects below the latter. The projecting portion is threaded as indicated at 94. Likewise strain rod 32 passes through an opening 95 in head S8 and has a projecting portion that is threaded as shown at 96.

It is evident that the upper chamber 56 extends between head 19 and partition 35 while lower chamber 57 lies between partition 35 and lower head S8.

An upper piston 97 reciprocates in chamber 56. It has an axial opening 98 (FIG. 2) which receives pump rod 29 with the latter being affixed thereto as by key ring 99. O ring 100 seals this connection. Piston 97 has a vertical passage 101 slidably receiving strain rod 31. O rings 102 seal the sliding t with the strain rod and O rings 103 the connection with cylinder 27. Another vertical passage 104 in piston 97 slidably receives strain rod 32 with O rings 105 sealing the connection.

A lower piston 106 reciprocates in lower chamber 57.

It is anchored to pump rod 29 and the connection sealed with an O ring in the same manner as piston 97. It also slides on strain rods 31 and 32 with these connections as well as that with the bore of cylinder 27 in the same way as described in conjunction with oistoi 97.

In operation as air under pressure is delivered to the upper chamber 56 between partition 35 and piston 97 1t 1s exhausted from the lower chamber 57, this condition being depicted in FIG. 6. Both the pistons 97 and 106 move upwardly together. As piston 106 approaches partition 35 it engages springs 55 and 82 to compress and store up energy in these springs until piston 106 bodily engages part 49 of valve V and sleeve 81 of valve I. This causes the valves V and I to move over quickly to their opposite positions. This movement is caused by the piston travel as supplemented by spring action. Air under pressure is now delivered to the lower chamber 57 between partition 35 and piston 106 and is exhausted from the upper chamber.

THE SPACER The spacer S is interposed between the actuator A and pumping assembly P. It is illustrated in detail in FIG. 4b. Referring to this figure a lower spacer end is depicted at 107. A rod 108 has one end secured to the upper face of end 107 as by welding 109. Its upper end takes the form of a threaded socket 110 into which is screwed the threaded end portion 96 of strain rod 32.

Another spacer rod 111 has one end welded to spacer end 107 at 112 and has a threaded socket 113 at its upper end receiving threaded end 94 of strain rod 31.

Spacer end 107 has a central opening in which pump rod 29 reciprocates. O rings 115 seal this connection. Opening 114 is enlarged on the upper face of spacer end 107 as indicated at 116 and one end of a central spacer tube 117 is tted in enlarged opening 116. The upper end of tube 117 is seated in an enlargement 118 of opening in actuator head 88.

The spacer end 107 is formed on its lower face with a recess 119 which extends to opening 114.

THE PUMPING ASSEMBLY Referring now to FIGS. 4c and 9 the pumping assembly P will be described. A ring 120 is secured in face to face engagement with the lower face of spacer end 107 as by welding 121. Fitted within ring 120- is a pumping cylinder 122 the upper end of which abuts the lower face of spacer end 107. Ring 120` closes recess 119 and is formed with a counterbore 123 which cooperates with recess 119 in dening a valve chamber. Seat ring 124 is fitted in counterbore 123 and a ball valve 125 c0- operates with the valve seat provided by ring 124. It is evident that the valve chamber provided by recess 119 communicates with the interior of cylinder 122.

A lower pump ring 126 receives the lower end of cylinder 122 and the connection is secured as by welding 127. A valve cage 128 is secured toy the lower face of ring 126 and the connection sealed by O ring 129. Valve cage 128 has a central plug 130 that is fitted in the lower end of cylinder 122 to close the latter. This plug 130` delines an annular chamber 131. Cage 128 carries a downardly projecting stem 132 having a bore 133. Bore 133 and chamber 131 communicate via angular radial passages 134.

Plug is formed with a central passage 135 communicating between bore 133 and interior of cylinder 122. Passage 135 is stepped at two places. One of these steps receives a seat ring 136 and the other a ball retainer 137., A ball valve 138 cooperates with the seat of ring 136 and is maintained in operating relation thereto by retainer 137.

A so-called bypass tube 139 has its upper end anchored to ring 120 as by welding 140 with its bore aligning with opening 141 which is enlarged to form counterbore 123. The lower end of tube 139 is secured to ring 126 as by welding 142 with its bore in alignment with an opening 143 that communicates with chamber 131.

A pumping piston 144 has an outside diameter slightly less than the diameter of the bore of cylinder 122 in which it reciprocates. The outer cylindrical suruface of piston 144 is formed with a series of annular grooves 145, 146, 147, 148, 149 and 150. It is also formed with an axial passage 151 closed at its lower end and terminating at its upper end in a threaded counterbore 152. Pump rod 29 terminates in a threaded portion 153 that is screwed into counterbore 152. A flange 154 integral with pump rod 29 has an outer diameter the same as that of piston 144. It is in abutting engagement with the upper face of the piston.

A plurality of angularly spaced radial passages 155 communicate between groove 146 and axial passage 151. Likewise a plurality of radial passages 156 communicate between groove 149 and passage 151. An O ring is assembled in iloating position in each of the grooves to 150. These O rings are designated 155, 156, 157, 158, 159 and 160. While they oat in the grooves their outside diameter is dimensioned so that they are normally 1n sealing engagement with the bore of cylinder 122. They function as check valves depending upon the direct1on of movement of the piston 144 which together with fluid action causes the O rings -160 to assure either a position free of the side Walls of the grooves, or a position in which any of them may be in sealing engagement with the side wall of a groove.

In describing the operation of the pumping assembly it will be assumed that the stern 132 is immersed in the oil in the well bottom and the actuator A causes reciprocation of pumping piston 144. FIG. 9 depicts the condition as the piston 144 approaches the end of a downward stroke. This stroke will have caused the ball valve 125 to unseat from the ring 124 to permit oil to be drawn from the bypas's tube 139 into cylinder 122 above piston 144.

Upon the upward stroke the oil moves the O ring 160 away from its sealing engagement with the side wall of groove 150. Thus the oil passes within the O ring 160 to the groove 149 where it also breaks the seal of O ring 159 from the upper side of groove 149 to permit the oil to enter radial passages 156 and from them pass to the axial passage 151 and thence through the bore of pump rod 29. During this upward stroke oil is prevented from escaping out of passages 155 due to the fact that O rings 155 and 156 are in sealing engagement with the lower side walls of grooves 145 and 146.

This upward stroke seats the ball valve 125 on seat ring 124 and at the same time unseats ball valve 138 from seat ring 136. Thus oil is drawn from bore 133 of cage stem 132 into cylinder 122.

On the down stroke the opposite of the above pumping action takes place. Oil from below piston 144 displaces O rings 155 and 156 from their sealing engagement with the side walls of grooves 145 and 146 to permit the oil to flow about the O rings and through passages 155 to axial passage 151. As this occurs any tendency of the oil to ilow out of radial passages 156 is precluded by the IO rings 159 and 160 again assuming their sealing position.

While the O rings 157 and 158 are not essential to the pumping action above described they are provided to definitely assure that any oil which might pass O ring 159 on the upward stroke or the O ring 156 on the down stroke goes no further. Thus should any oil get past the O ring 159 on the upstroke it will move the O ring 15S into sealing engagement with a side wall of groove 148 and prevent any further downward travel of the oil.

While preferred speciiic embodiments of the invention are hereinbefore set forth, it is to be clearly understood that the invention is not to be limited to the exact embodiments illustrated and described because various modifications of the details may be provided in putting the invention into practice within the purview of the appended claims.

What is claimed is:

1. In a pump for installation at the bottom of an oil well casing having an oil delivery conduit and operable by air under pressure from an air line in the casing, an actuator comprising upper and lower heads, a cylinder secured to said heads, a partition aiiixed to said Acylinder midway of said heads, a pair of hollow strain rods extending between said heads and disposed in diametrically opposed relation, said partition defining upper and lower chambers, a piston in each chamber slidable on said strain rods, a tubular pump rod extending through said cylinder in sliding relation to said heads and partition, said pump rod projecting into said oil delivery conduit, an air supply line in one strain rod terminating at said partition, an air inlet valve in said partition for alternately delivering air under pressure to said chambers, an exhaust connecting with the other of said strain rods, an exhaust valve in said partition for alternately exhausting air from said chambers, and springs carried by each of said valves at the opposite ends thereof for engagement by said pistons to move said valves from one position to the other; and a pumping assembly below said actuator and comprising a pumping cylinder, a pumping piston reciprocal in said pumping cylinder and connected to the lower end of said pump rod, a valve cage at the lower end of said pumping cylinder, a check valve in said cage controlling communication from the well bottom into said pumping cylinder, a bypass tube extending from said valve cage to the upper end of said pumping cylinder, a check valve at the upper end of said bypass tube, said pumping piston being formed with an annular groove; and an O ring in said groove in floating relation to the side walls thereof and normally in sealing engagement with the bore of said pumping cylinder, said piston having an axial passage communicating with said pump end and radial passages between said groove and axial passage, said O ring constituting a check valve.

2. The pump of claim 1 in which there is a spacer between said actuator and said pumping assembly, said spacer comprising a tube through which said pump rod passes and a plurality of spacer rods about said tube.

3. The pump of claim 1 together with a supply of air under pressure at the surface of the earth in which the well is located and in which the exhaust terminates at a point above the level of oil in the well.

4. The pump of claim 2 in which the spacer has a lower end formed with a downwardly opening recess that cooperates with the upper end of the bypass tube in deiining a valve chamber that communicates with the interior of said pumping cylinder.

5. In a bottom of the well oil pump, actuator mechanism comprising: an upper head, a lower head, a cylinder having its opposite ends secured to said heads, a pair of hollow strain rods in diametrically opposed relation and extending between said heads, a horizontal partition aixed to said cylinder and defining upper and lower chambers, an air inlet line passing through said upper head into one of said strain rods and terminating at said partition, an exhaust connected to the other of said strain rods at said upper head, a tubular pump rod in sliding relation to said heads and partition, a piston reciprocal in each of said chambers, each of said pistons being secured to said pump rod and in sliding relation to said strain rods, an air inlet valve in said partition alternately delivering air to said chambers, a spring at each end of said valve projecting therefrom and adapted to be engaged by one of said pistons, an exhaust valve in said partition alternately exhausting air from said chambers to said exhaust, and a spring projecting from each end of said exhaust valve and adapted to be engaged by one of said pistons, whereby each valve is moved from one position to the other by bodily engagement with a piston and the action of the spring which has been compressed by the piston.

6. The pump actuator of claim 5 in which the air inlet valve comprises a central body of maximum diameter and shanks of reduced diameter extending from the opposite ends thereof with the springs being seated in the shanks.

7. The pump actuator of claim 5 in which the exhaust valve is a spool valve having heads in which the springs are seated.

8. In a pumping assembly designed for installation in a well bottom, an upper ring attachable to structures thereabove, a pumping cylinder having its upper end anchored to and within said ring, a valve cage secured to the lower end of said cylinder and having a plug received in said cylinder, said valve cage presenting an annular chamber, said plug having a central passage, a check valve operably mounted in said plug and controlling the flow of oil through said passage to said cylinder, a bypass tube having its lower end communicating with said chamber and its upper end with the upper end of said cylinder, a check valve at the upper end of said bypass tube, a tubular pump rod extending into said cylinder from the upper end thereof, a piston reciprocal in said cylinder and having an axial passage communicating with said pump rod and closed at its lower end, said piston having an annular groove, radial passages between said groove and axial passage, and a check valve in the form an O ring in said groove in floating relation to the side walls of the groove and in sealing engagement with the bore of said cylinder.

9. The pumping assembly of claim 8 in which there are a plurality of annular grooves and an O ring iioating in each groove, and two sets of radial passages longitudinally spaced apart in said piston, one set communicating with one groove and the other set with another groove.

10. The pumping assembly of claim 8 in which the check valves in the valve cage and at the upper end of the bypass tube are ball valves.

11. The pumping assembly of claim 8 in which the structure above the ring is formed with a downwardly opening recess that cooperates with a counterbore in the ring to define a valve chamber communicating with the 10 bore of the cylinder and the check valve at the upper end of the bypass tube takes the form of a ball valve in said last mentioned chamber.

12. The pumping assembly of claim 8 in which there are six annular grooves in the piston and two sets of 15 References Cited UNITED STATES PATENTS `6/1925 Todd 103-46 1/1931 Ekstromer 103-46 ROBERT M. WALKER, Primary Examiner U.S. C1. X.R. 

